This invention relates to a cutter for a shaper and, more particularly, to a cutter for cutting irregular shapes such as the teeth of a gear. Customarily, such cutters include a body with a plurality of teeth spaced angularly around the periphery of the body. The ends, sides and roots of the teeth are inclined radially inwardly from the face of the body so that the edges of the teeth constitute the cutting edges of the cutter. Frequently, the cutter is surface coated as with a thin film of titanium nitride.
When the cutting edges of most present commercially used shaper cutters become dull, they are resharpened by grinding the face of the tool and hence the faces of the teeth. Such grinding presents a number of difficulties. My U.S. Pat. No. 4,576,527 discloses a shaper cutter which overcomes these difficulties. In the cutter disclosed in that patent, teeth with cutting edges are formed on a thin flexible wafer which is attached to and conforms with the teeth and face of a tool holder, the latter being basically the same as the cutting body of prior cutters and serving to back the cutting teeth of the wafer. When the cutting edges become dull, the thin wafer is simply removed and replaced with a new one. To attach the wafer to the body in conformity with the teeth and face thereof, provision is made of a clamping ring adapted to lie against the end face of the wafer. When a fastener is tightened, the clamping ring flexes the thin wafer into conformity with the tool body and clamps the wafer and the body in assembed relationship.
Even though the wafer is clamped to the body, means must be provided for anchoring the wafer in a precisely fixed angular position and for preventing the wafer from turning on the body. In the cutter of my prior patent, such turning is prevented by a cylindrical locating pin which projects through a hole in the clamping ring and into notches in the wafer and the body. This arrangement suffers, however, by virtue of the fact that the engagement between the pin and the flexed or deflected wafer is, for all practical purposes, only line contact around a maximum of 90 degrees of the circumference of the pin. Such limited contact between the pin and the edge of the hole in the wafer causes deformation in the interlock region when the wafer is subjected to tangential cutting forces. The deformation allows the wafer to shift angularly relative to the body to such an extent that the backup normally provided by the teeth of the body is lost, thereby leading to premature failure of the wafer.
In an effort to overcome the deficiencies of the angular interlock disclosed in the aforementioned patent, use has been made of an interlock comprising a special key of rectangular cross-section. Such a key fits into keyways in the wafer, the body and the clamping ring and, because of its special shape, has improved contact area with the deflected wafer so as to minimize angular creep of the wafer in most applications. This design, however, requires very tight tolerances to be held on the key and the keyways and thus is expensive to manufacture. Moreover, other design considerations dictate that the keyway in the wafer have sharp corners. This creates stress risers which, in some cases, has led to fracture of the wafers when the wafers are deflected.